Microfabricated vertical comb actuator using plastic deformation

Abstract

A microfabricated actuator of the vertical comb-drive (AVC) type or staggered vertical comb-drive type for torsional or linear applications includes torsion springs which permit self-aligned deformation of the device (micromirror) structure of the actuator through the heating of the torsional springs to plasticity. The torsional springs can include perpendicular-beam springs or double folded beams which allow axial movement of the spring when heated. Heating of the springs can be by bulk heating of the actuator structure or by Joule heating to the torsional springs by passing an electrical current therethrough.

1. A vertical comb-drive actuator comprising:
 a) a support structure, 
 b) a planar device structure, 
 c) a plurality of torsion springs physically coupling the device structure to the support structure, the torsion springs being movable on deflecting the device structure in response to electrical actuation, each torsion spring having an end portion for joining the support structure which permits axial movement of the torsion spring in response to thermal expansion of the torsion spring during fabrication, said end portion further comprising double folded beams for coupling the device structure to the support structure, the double folded beams including first and second beam members coupling the device structure to an apex and third and fourth beams coupling the apex to the support structure. 
 
   
   
     2. The actuator as defined by  claim 1  wherein the device structure includes a first plurality of combs and the support structure includes a second plurality of combs which are interdigitated with the first plurality of combs and which cooperatively drive the device structure in response to electrical actuation. 
   
   
     3. The actuator as defined by  claim 1  wherein the actuator comprises semiconductor material. 
   
   
     4. The actuator as defined by  claim 3  wherein the device structure and the torsion springs comprise doped silicon. 
   
   
     5. The actuator as defined by  claim 4  wherein the actuator comprises a silicon on insulator substrate. 
   
   
     6. The actuator as defined by  claim 4  wherein the device structure includes a first plurality of combs and the support structure includes a second plurality of combs which are interdigitated with the first plurality of combs and which cooperatively drive the device structure in response to electrical actuation. 
   
   
     7. The actuator as defined by  claim 4  wherein the actuator comprises an angular vertical comb-drive actuator. 
   
   
     8. The actuator as defined by  claim 4  wherein the actuator comprises a staggered vertical comb-drive actuator. 
   
   
     9. The actuator as defined by  claim 4  wherein the actuator comprises a torsional actuator. 
   
   
     10. The actuator as defined by  claim 4  wherein the actuator comprises a linear actuator.